The present invention relates to devices and methods suitable for treating fecal incontinence. Fecal incontinence (also referred to as anal or rectal incontinence or accidental bowel leakage) is a disorder afflicting both children and adults with devastating social and psychological affects. It is estimated that in the United States alone more than 5.5 million individuals suffer from fecal incontinence and that the incidence rate of this disorder is 1-5%. Fecal incontinence is a major factor limiting the rehabilitation of the elderly and disabled, preventing many of them from being cared for at home. Mild to moderate incontinence accounts for about 80% of the market (gas, liquid and soiling) while severe incontinence accounts for the remaining 20%.
Fecal continence results from a coordinated motor function of anal sphincters and pelvic floor muscles, the role of the rectum and sigmoid colon as a fecal reservoir with capacitance and compliance and as a propulsive force with intrinsic motor activity, the effects of stool consistency, volume and delivery rate, the anorectal angle, and anorectal sensation.
The most common causes of fecal incontinence are structural or functional deficiencies of the sphincter muscles. Such deficiencies can result from anatomic disruption of the sphincter mechanism which may be caused by obstetric injuries (perineal laceration and improperly performed median episiotomies), complications of hemorrhoid, fistula or fissure surgery (keyhole deformities), traumatic injuries (e.g., impalement injuries), or cancer or from deterioration of the sphincter muscles due to age, congenital disorders, systemic and metabolic diseases, acquired neurological defects, and diseases of the colon and rectum.
Anal sphincters are muscular structures that assist in controlling the flow of feces and release of flatus from the colon. The internal anal sphincter (IAS) and the external anal sphincter (EAS) encircle the anal canal and form a part of the anorectal ring (see FIG. 1). The IAS is a thickening of the gastrointestinal smooth muscle; it maintains continence at rest. The EAS is composed of striated, voluntary muscle. The EAS, the puborectalis, and the levator ani muscles work in concert to prevent leakage of flatus and feces when there is an increase in abdominal pressure or when the internal anal sphincter relaxes after rectal distention.
Resting pressure in the anal canal is typically 60 mm Hg (1.1 psi), increasing up 5 to 100 mm HG (1.9 psi) in strain or forced exertion. In a normal individual (normal parameters vary widely), the myogenic activity of the involuntary internal sphincter contributes about 10% of the anal resting pressure, and 45% is due to the sympathetic innervation of the internal sphincter, for a total of 55%. The remainder of the resting tone is from the hemorrhoidal plexus (15%) and the external anal sphincter (30%). The 10 external sphincter supplies 100% of the voluntary short-term squeeze pressure. Therefore, what is needed to improve continence is a technology that can influence the ability of the anus to seal better in the resting state while not interfering with the distention function of the sphincter during defecation.
Present treatment approaches for restoring fecal continence include non-surgical and surgical therapy. Non-surgical therapy for incontinence include biofeedback and perineal strengthening exercises beneficial in alleviating symptoms of seepage and occasional loss of control and electrical stimulation to improve contraction of the sphincter muscles.
Surgical therapy approaches include implantation of artificial valves (see, for example, U.S. Pat. Nos. 6,471,635, 6,749,556, and U.S. patent application Ser. Nos. 10/269,949 and 10/651,851), injection of bulking agents into the anal mucosa or the anal sphincters (see, for example, Vaizey and Kamm, British Journal of Surgery 2005; 92: 521-527), implanted electrodes for stimulating the pudendal or sacral nerves (see, for example, U.S. Pat. Nos. 6,907,293 and 7,054,689) or sphincteric muscles (see, for example, PCT publication No. WO06047833).
Fecal incontinence can also be partially controlled using absorbent pads, absorbent plugs or hard plugs/valves and the like, however, such approaches are not well tolerated by individuals due to efficacy, convenience and comfort limitations as well as sealing limitations.
Thus, there remains a need for a device and method for treating fecal incontinence which are devoid of the above limitations.